Question

Assuming gasoline is pure${\text{C}}_{\text{8}}{\text{H}}_{\text{18}}\left(\text{L}\right)$ predict the signs of qandw for the process of combusting gasoline into ${\text{CO}}_2\left(g\right)$and ${\text{H}}_2\text{O}\left(g\right)$.

Short answer

Signs of both q and w will be negative.

Step-by-step solution

 STEP 1: About combustion.

The combustion is a process of chemical combination of a substance with oxygen involving the production of heat and light.

$\text{Gasoline}+O_2\to {\text{CO}}_{\text{2}}\uparrow +{\text{H}}_{\text{2}}\text{O}\uparrow$

STEP 2:Explanation.

The process of combusting pure gasoline ${\text{C}}_{\text{8}}{\text{H}}_{\text{18}}$.

$$\begin{gathered} {\text{C}}_{\text{8}}{\text{H}}_{\text{18}}+{\text{O}}_2\to {\text{CO}}_{\text{2}}\uparrow +{\text{H}}_{\text{2}}\text{O}\uparrow +\Delta \left(\text{heat}\right) \\ \text{octane} \end{gathered}$$

Here, the surrounding is gaining heat from the system, and the temperature of the surrounding increases. Therefore,q is exothermic and negative.

As the work done by any system loses energy, therefore the sign of w is also negative.